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Nuclear Theory·nucl-th

Thursday·June 23, 2022

5 papers—3 primary·2 cross-listed

All5Primary3Cross-lists2
  1. 01

    [Submitted on 21 Jun 2022]

    QED medium effects in (anti)neutrino-nucleus and electron-nucleus scattering: elastic scattering on nucleons

    Oleksandr Tomalak🇺🇸 · Ivan Vitev🇺🇸

    Interpretation of current and future neutrino oscillation and electron scattering experiments requires knowledge of lepton-nucleon and lepton-nucleus interactions at the percent level. We study the exchange of photons between charged particles and the nuclear medium for (anti)neutrino-, electron-, and muon-induced reactions inside a large nucleus. While quantum electrodynamics (QED)-medium contributions are formally suppressed by two powers of the electromagnetic coupling constant when compared to the leading-order cross sections, low-energy modes and the nuclear size enhance the effect by orders of magnitude. They require a proper infrared regularization, which we implement as a screening of the electromagnetic interactions at atomic length scales or above. We provide approximate analytic expressions for the distortion of (anti)neutrino-nucleus and charged lepton-nucleus cross sections and evaluate the QED-medium effects for realistic values of the screening scale on the example of elastic scattering with nucleons inside the nucleus. We find new permille- to percent-level effects, which were not considered in either (anti)neutrino-nucleus or electron-nucleus scattering.

    Comments:
    18 pages, 10 figures, v2: version published in Physics Letters B, plots for different beam energies added to new Appendix B
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2206.10637 [pdf]
    PLB(2022)·9 citations
  2. 02

    [Submitted on 21 Jun 2022]

    The Entanglement Entropy between Short Range Correlations and the Fermi Sea in Nuclear Structure

    Ehoud Pazy

    We calculate the nuclear structure orbital entanglement entropy of short range correlations (SRC) based on the nuclear scale separation. Specifically, the entanglement between the SRC orbitals and the rest of the system. It should be stressed that this is a single nucleon not a pair entanglement entropy between the proton and neutron. The entanglement arises from the probability for a nucleon to occupy a momentum state above the Fermi momentum. We separate the momentum space of the nucleus into two parts such that nucleons can occupy the meanfield part of the wave function, i.e. Fermi sea (FS) and separately the high-momentum SRC part. The orbital entropy we obtain is between these two parts where we essentially define two momentum subspaces, one containing all the low momentum FS states and the other the high-momentum part as a SRC "orbital" state. For the calculation we employ the decoupling of low and high-momenta which was established by the similarity normalization group the SRC is viewed as a further "orbital" which can be multiply occupied. Since the probability of the occupation of a single SRC is given by the nuclear contact we are able to obtain a simple general expression of the orbital entanglement entropy for SRC by employing the generalized contact formalism. This general formula for the SRC orbital entanglement entropy of a nuclear structure in terms of the nuclear contact, allows us to obtain the scaling of the entropy in terms the mass number, . We find that, unlike the entanglement entropy of many quantum systems which scales with the surface area, the orbital entanglement entropy associated with the SRC in large nuclei is linearly dependent on , i.e., it is shown to be extensive.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2206.10702 [pdf]
    PRC(2023)·37 citations
  3. 03

    [Submitted on 21 Jun 2022]

    Probing high-density nuclear symmetry energy with ratio in heavy-ion collisions at GeV

    Gao-Chan Yong🇨🇳 · Bao-An Li🇺🇸 · Zhi-Gang Xiao🇨🇳 · Zi-Wei Lin🇺🇸

    Recent beam energy scan (BES) experiments at RHIC by the STAR Collaboration (PLB {\bf 827},137003 (2022) and PRL {\bf 128}, 202303 (2022)) found that hadronic interactions dominate the collective flow and the proton cumulant ratios are driven by baryon number conservation in a region of high baryon density in = 3 GeV Au+Au reactions, indicating the dense medium formed in such collisions is likely hadronic matter. Within an updated ART (A Relativistic Transport) model with momentum dependent isoscalar and isovector single-nucleon mean-field potentials corresponding to different symmetry energies at suprasaturation densities, the , , , and ratios are studied for central Au+Au collisions at = 3 GeV where the maximum central density reaches about . The doubly strange ratio is found to have the strongest sensitivity to the variation of high-density nuclear symmetry energy. Thus, the ratio in relativistic heavy-ion reactions at GeV may help probe sensitively the poorly known symmetry energy of dense neutron-rich matter critically important for understanding various properties of neutron stars.

    Comments:
    With minor revisions. Phys. Rev. C in press
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
    arXiv:
    2206.10766 [pdf]
    PRC(2022)·31 citations
  4. 04

    [Submitted on 21 Jun 2022] (cross-list from nucl-ex)

    alpha-cluster structure of 18Ne

    M. Barbui🇺🇸 · A. Volya🇺🇸 · E. Aboud🇺🇸 · S. Ahn🇺🇸 · J. Bishop🇺🇸 · V.Z. Goldberg🇺🇸 · J. Hooker🇺🇸 · C.H. Hunt🇺🇸 · H. Jayatissa🇺🇸 · Tz. Kokalova🇬🇧 · E. Koshchiy🇺🇸 · S. Pirrie🇬🇧 and 6 other authors

    In this work we study alpha-clustering in 18Ne and compare it with what is known about clustering in the mirror nucleus 18O. The excitation function of 18Ne was measured in inverse kinematics from the resonant elastic scattering reaction of 14O on 4He in the excitation energy range from 8 to 17 MeV, using the active target TexAT. The analysis was performed using a multi-channel R-matrix approach. Detailed spectroscopic information is obtained from the R-matrix analysis: excitation energy of the states, spin and parity as well as partial alpha and total widths. This information is compared with theoretical models and previous data. Clustering structures appear to be robust and mostly isospin symmetric. A good correspondence was found between the levels in 18O and 18Ne. We carried out an extensive shell model analysis of the experimental data. This comparison suggests that strongly clustered states remain organized in relation to the corresponding reaction channel identified by the number of nodes in the relative alpha plus core wave function. The agreement between theory and experiment is very good and especially useful when it comes to understanding the clustering strength distribution. The comparison of the experimental data with theory shows that certain states, especially at high excitation energies, are significantly more clustered than predicted. This indicates that the structure of these states is collective and is aligned towards the corresponding alpha reaction channel.

    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2206.10659 [pdf]
    PRC(2022)·8 citations
  5. 05

    [Submitted on 22 Jun 2022] (cross-list from hep-ph)

    On the determination of uncertainties in parton densities

    N.T. Hunt-Smith🇦🇺 · A. Accardi🇺🇸 · W. Melnitchouk🇺🇸 · N. Sato🇺🇸 · A.W. Thomas🇦🇺 · M.J. White🇦🇺

    We review various methods used to estimate uncertainties in quantum correlation functions, such as parton distribution functions (PDFs). Using a toy model of a PDF, we compare the uncertainty estimates yielded by the traditional Hessian and data resampling methods, as well as from explicitly Bayesian analyses using nested sampling or hybrid Markov chain Monte Carlo techniques. We investigate how uncertainty bands derived from neural network approaches depend on details of the network training, and how they compare to the uncertainties obtained from more traditional methods with a specific underlying parametrization. Our results show that utilizing a neural network on a simplified example of PDF data has the potential to inflate uncertainties, in part due to the cross validation procedure that is generally used to avoid overfitting data.

    Comments:
    32 pages, 9 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    2206.10782 [pdf]
    PRD(2022)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE